Method of determining the load on a vehicle occupant

#The invention relates to a method for determining the load acting on the body of a vehicle occupant restrained by a seat belt, wherein electrical signals from occupant restraint device sensors are evaluated in an evaluating device.

#DE 297 17 477 U1 teaches a seat belt retractor in which the winding state of the seat belt is determined by a belt reel sensor, which, acting as an incremental sensor, detects the rotational position of the belt reel. The corresponding signals are fed together with other sensor signals to an electronic unit present in the vehicle, which contains a microcomputer with microprocessor and associated memories, for evaluation of the signals. Depending on the signal evaluation, given safety devices of the vehicle occupant restraint system, such as a belt tightener, an airbag, a belt buckle and the like are actuated.

#It is known from WO 85/04628 to trigger the blocking device, with which the belt reel is blocked in the seat belt retractor, as a function of rotational angle signals that are obtained from scanning of the belt reel.

#FIG. 1 is a block diagram of an exemplary embodiment of a device with which the invention may be performed.

#FIG. 2A is a graphic representation of the change over time in the rotational angle of the belt reel in the event of a major crash.

#FIG. 2B is a graphic representation of the change over time in the rotational angle speed of the belt reel in the event of a major crash.

#FIG. 1 is a block diagram of an exemplary embodiment of a device with which the invention may be performed. A belt reel 1 is arranged in a seat belt retractor 13, in particular a seat belt retractor that is a component of a three-point seat belt system of a motor vehicle, for retraction and extraction of seat belt webbing 15. Torque from a belt tightener drive, in particular an electric motor 14 is transmitted to the belt reel 1 via a rotor 2. The rotor 2 is preferably the rotor of the electric motor 14, but may be a rotor arranged outside the belt tightener drive. A torque transmission device 7, which may take the form of a clutch, a gear and the like, is located between the rotor 2 and the belt reel 1. The torque transmission device 7 may be externally controlled or automatically switchable. The torque transmission device may comprise a damping device with particular damping behavior.

#The drive force generated by a belt tightener may be transmitted to the belt reel with particular damping behavior, exhibited by the force transmission section between belt tightener and belt reel. From determination of the belt webbing movement, in particular in the webbing take-up direction or by scanning the rotational angle of the belt reel, and the known damping behavior of the force transmission section, the force or load exerted by the seat belt on the vehicle occupant may be determined. The force limiting behavior of a belt force limiter may be adjusted as a function thereof.

#In the exemplary embodiment, a rotational angle sensor 5 is provided for scanning the extraction or take-up movement of the seat belt webbing 15, which is not shown in any more detail. The rotational angle sensor 5 supplies electrical signals to an evaluating device 3 that are proportional to the respective rotational angles of the belt reel 1.